Bug 1497299 - Avoid destroying nsHashPropertyBag when recording/replaying, r=mccr8.

Differential Revision: https://phabricator.services.mozilla.com/D22561

--HG--
extra : moz-landing-system : lando

xpcom/ds/nsHashPropertyBag.h

@@ -32,7 +32,12 @@ class nsHashPropertyBagBase : public nsIWritablePropertyBag,
 
 class nsHashPropertyBag : public nsHashPropertyBagBase {
  public:
-  nsHashPropertyBag() {}
+  nsHashPropertyBag() {
+    // Avoid destroying this object when recording/replaying. See bug 1497299.
+    if (mozilla::recordreplay::IsRecordingOrReplaying()) {
+      AddRef();
+    }
+  }
   NS_DECL_THREADSAFE_ISUPPORTS
 
  protected: